The present invention relates to a method for improving the thermal stability of polyphenylene ethers and to polyphenylene ethers having terminal anthranilate ester groups obtained therefrom.
As shown in copending application, Ser. No. 028,857, filed Mar. 23, 1987, assigned to the same assignee as the present invention and incorporated herein by reference, polyphenylene ethers having improved heat stability can be made by end-capping the polyphenylene ether in the melt with a salicylic acid ester. Experience has shown that end capping of polyphenylene ether can preclude, or reduce undesirable cross-linking of the polyphenylene ether, or undesirable interactions between the polyphenylene ether and another polymer. It is, therefore, desirable to provide alternate techniques for end capping polyphenylene ethers to enhance the thermal stability of these polymers.
The present invention is based on our discovery that heating polyphenylene ether in the presence of isatoic anhydride and an inert organic solvent such as toluene, has been found to enhance the thermal stability of the resulting polyphenylene ether.